Thermophysical properties and CMAS corrosion behavior of high-entropy RE3NbO7-type rare-earth niobate ceramic

To address the pressing demands of next-generation aero-engines for thermal barrier coatings (TBCs) with low thermal conductivity, high thermal expansion compatibility, and CMAS corrosion resistance, a high-entropy engineered rare earth niobate ceramic, (Gd 0.2 Ho 0.2 Er 0.2 Tm 0.2 Yb 0.2 ) 3 NbO 7 (GHETY), was designed and synthesized. The material exhibits a stable single-phase defective fluorite structure with ultralow thermal conductivity (1.169 W·m −1 ·K −1 at 25 °C) due to enhanced phonon scattering from configurational entropy and lattice disorder. It also shows a high thermal expansion coefficient (10.879 × 10 −6 K −1 at 1200 °C), ensuring good thermal compatibility for TBC applications. Corrosion tests at 1300 °C show that GHETY reacts with molten CMAS to form apatite and RENbO 4 phases. The formation of RENbO 4 depends on both corrosion duration and CMAS supply, with a reaction layer reaching 190.37 μm at 20 h under 50 mg/cm 2 loading. The detailed corrosion behavior observed in this study provides valuable insights into the CMAS corrosion mechanisms of high-entropy rare-earth niobates. These findings highlight the potential of entropy-engineered niobates as candidates for chemically stable and thermally compliant TBCs, offering a promising pathway for next-generation thermal protection systems.